Communication system



July 21, 1936. A, 5, mass COMMUNICATION SYSTEM 2 Sheets-Sheet 1 Filed April 29, 1935 INVENTOR 16m 5.

TcSRNEY i July 21, 1936. A. s. RIGGS 2,048,081

COMMUNI CATION SYSTEM Filed April 29, 1933 2 Sheets-Sheet 2 "qzgi-l #5 5 j m 5 5 n n n AAMAAAAA L15 7 A6 L INVENTOR IS ATToNEY Patented July 21, 1936 umrao STATES PATENT OFFICE COMMUNICATION SYSTEM Alger S. Riggs, New York, N. Y.

A Application April 29, 1933, Serial No. 668,503

- 7 Claims.

sion of a system of communication whereby a.

multiplicity of separate and distinct communicaent invention is the provision of means for automatically maintaining synchronism between the transmitter and receiver in a communication system of the character herein disclosed.

15 Although I have herein shown and described but one form of my invention as applied to the transmission of a multiplicity of signals of telephonic nature, I do not limit myself thereto, inasmuch as modifications and changes may be 20 made in the character and use of this invention without departing from the original spirit of the invention or the scope of the appended claims.

Referring to the drawings,

Fig. 1 is a. diagrammatic view of one form of the 25 present invention as adapted to the simultaneous transmission and reception of a plurality of sig-' nals of telephonic nature over one transmission line or medium.

Fig. 2 is a diagrammatic representation of the 30 sequence-controlling apparatus and circuit as used at the transmitter.

Fig. 3 is a diagrammatic representation of the sequence-controlling apparatus and circuit as used at the receiver.

35 Fig. 4 is a diagram by whichthe mode of operation of the present invention may be readily understood.

Throughout the following, like characters are used to represent the same pieces of apparatus.

40 Where an electron-discharge device having several internal electrodes is referred to, the characters K, G1, G2, G3 and P shall refer respectively to the cathode, grid next adjacent the cathode, second grid, third grid and plate, irrespective of the normal or especial functions of such electrode.

Referring to Fig. 1, the transmitter consists of a plurality of electron-discharge devices,'

cally on the drawings to the right of the line coupling transformer Ta. 7

In order tomore readily understand the method of operation of the present invention, and to clearly discriminate between its mode of operation and that of conventional systems for multi-signal communication, it should be understood that in the conventional transmission or amplification of an electrical signaLthe system is made to produce at its output an enlarged replica of the input sig- 10 nal wave form. The present invention does not contemplate transmission of the complete wave form or cycle of'the signal, but of transmitting in rapid sequence, measurements of the signal voltage at spaced instants of transmission. At 5 the receiveing apparatus, the received impulses, which represent progressive and rapidly recurring or periodic amplitude measurements of the signal, each preferably of very short duration, are impressed upon a device or apparatus having appreciable relative time lag or inertia (mechanical or electrical), which may be referred to as an integrating device. whereby the received impulses are in effect added or integrated into a resultant which reproduces the original wave form to a remarkable degree of accuracy. The more rapid the impulse speed with relation to the rate of change of signal characteristics (voltage), the nearer is the received and integrated signal a replica of the wave form impressed upon the transmitter and the more instantaneous the time of measurement the greater numberv of signal sources or programs that may be simultaneously transmitted over a single transmitting medium.

By using speeds of radio frequency, a. plurality of musical programs (for instance) can be transmitted over the same line or radio frequency band simultaneously.

Referring to Fig. 1, I have shown a plurality of signal sources (for example, four) connected to respective transformers T1--4, the secondaries of which are connected respectively to the third I grids G3 of the tubes V1-4, the plates P of which are connected together to a wire W which is also common to tubes V5 and V6 and is supplied with potential from source B: through the primary L1 of the transformerTs. The secondary L2 of the transformer T5 is connected to the transmission medium, herein shown as a concentric-conductor cableline. Obviously other known transmitting media may be employed, such as a modulator of a radio transmitter. 1

Through means described hereinafter} the tubes V1-4 are normally held inoperative and are rendered operative in rotation by the voltages supplied through conductors l-l from the sequence selectors shown in detail in Fig. 2.

Through the medium of the voltages supplied by the sequence selector, preferably to the suppressor grids shown at G1, the tubes V1-4 are rendered operative in a predetermined sequence and deliver to the line through the transformer T5 8. series of impulses which represent the amplitudes of the respective signals upon T14 at the instant their respective tubes are rendered operable. By using electron-discharge devices of the variety commonly known as pentode or three grid type and applying the synchronizing or conditioning potential to the first grids G1, I secure from the output a signal of a fixed time interval independently of the magnitude of the signal to be transmitted. With such tubes, I effectively.

shield the conditioning" and signal potentials from each other, i. e. from intra-capacity effects by the well understood action of the second grids G: which herein are used as screens by connecting all of said grids G1 to a point of fixed potential such as some point in battery 13:.

Means are also provided to synchronize the receiver and sending instruments preferably through the transmitted signals themselves. To this end I provide an additional tube V5. The tubes V4-5 are preferably so interconnected that they are rendered operable during the same time interval so that their output is added but no signal is impressed upon V5 and hence it delivers to the line an impulse of constant magnitude (preferably greater than any of the tubes V1-4) which is intercepted at the receiving device for the 'purpose' of indexing or controlling the sequence-selector S at the receiver.

The impulses transmitted, therefore, may be represented by the diagram of Fig. 4, the rectangle l' representing an impulse from tube V1, rectangle 3' an impulse from tube V3, 2' representing the same from the tube V2, and 4' representing the combined impulses from tube V5 (represented by the shaded portion of the rectangle 4', and the unshaded portion added by tube V4). The amplitude of the impulses from tubes V1, V2 and V3 never rises above dotted line 6, which lies below the top of the shaded portionof rectangle 4', shown by line 1.

The series of signal impulses received by the transformer T6 are impressed upon the third grids Go of tubes V7-l0, which are biased with respect to the several cathodes by battery Ba,'

and upon the plate or anode P of the tube V11.

Through the medium of the sequence-selector S, shown in Fig. 3, the tubes V11o are rendered operable in regularand synchronized sequence at such instants as to permit the respective tubes to deliver a signal impulse in its output circuit which is proportional to the original signal impressed upon the corresponding tube at the transmitter. The rapid radio frequency signals from each tube are impressed on their respective transformers T-z-m, but said transformers possess sufficient electrical inertia so that they respond only to the main variations in the output of the tubes. In other words, the transformers act to integrate or smooth out'the rapid spaced signals into audio frequency signals. Thus the transformers T'I-lfl each deliver a separate signal corresponding to those impressed upon the transmitter successively through tubes V1-4.

The tube Vs at the transmitter and the tube V11 at the receiver serve the function of preventing surge voltages respectively across L1 and L4 by quick quenching of the, secondary oscillations. The transmitted and received impulses are prevented by tubes Va and V11 from becoming positive with respect to the respective cathodes of said tubes so that only voltages of the desired polarityexist across L1 and L1, respectively.

Tubes V6\ and V11 are, in effect, connected across primary L1 of transformer T5 and secondary L4 of transformer T6 7 respectively. In the former case, the anode of tube Va is connected to the anodes of tubes V1-5; the screen grid of tube Va is biased by connection to battery B2; and the other grids and the cathode in the tube are connected in common to the cathodes of tubes V1-a. Thus, the tube Vs affords a by-pass for surges in the system which would otherwise increase the positive potential of the plates of tubes V1 s and increase the currents therethrough, to the detriment of the operation the cathode are connected in common to the cathodes of tubes V'z-1o. Thus, the tube V11 affords a by-pass for surges in" the system which would otherwise make the control grids of tubes V-z-m positive with respect to their cathodes, and, therefore, increase the currents through those tubes. Surge voltages of opposite sign are suppressed at opposite ends of the system. Thus, surge voltages which are negative with respect to thetransmitter are positive with respect to the receiver and are by-passed at the receiver, and vice versa.

Referring now to Fig. 2, the selector generator E and sequence-selector S used at the transmitter consist of the tubes V11-14. The tube V1: together with the multi-wound transformer T11 operates as a generator of sinusoidal voltage waves which are impressed upon the resistance R1 and the variable condenser C1. Winding Le thereof serves as the main tank circuit of the generator, while L5 serves as feed-back grid excitation'of the tube V12. The inductance (secondary) Ln completes the output of the generator to the load R1 and C1. The voltages respectively across R1 and C1 are impressed upon the tubes V1341 of sequence selector S, and since these voltages are in quadrature relation the transformers T1z-1a supply to their respective terminals amplified voltages having quadrature relation. The terminal wires l-l connect respectively to the first grids G1 of the tubes V1 5 and the terminal wire 5 connects to the common cathode return of the tubes V1-s. The rectifying action of the tubes produces a direct current voltage across resistance R3 and condenser C2 of the polarity shown which effectively renders the tubes inoperable except duringthe period when the grids have impressed thereon substantially the peak voltage in the positive direction. A second resistance R1 may be used to effectively filter the tron oscillator arrangement operating under the control 01' the incoming impulse from tubes VH. The plate of tube V15 is connected to a source of potential B5 and one of the auxiliary grid electrodes of the tube V15 is charged at a higher potential than the plate by a portion of the source of potential Be. The tube V15 then will oscillate due to the well known phenomenon of secondary electron emission. This operation of the tube V15 is reinforced once every cycle by the extraordinary impulse transmitted through tubes Vi-S, and impressed on the control grid of tube V15 through conductor l2, thus maintaining synchronism in the system. The other impulses transmitted through tubes V1-s are of insufficient magnitude to exert any control upon the oscillator V15. The output wave of the oscillator V15 is impressed directly on the control grid of amplifier tube V18, the output circuit of which is tuned to resonance with the frequency of the oscillator V15 which is synchronized with and, therefore, equal to the frequency of the oscillator V12 at the transmitter.

Transformer T14, comprising inductive elements L12 and L13, couples the oscillation from the receiving selector generator E to the sequence selector circuits shown generally at S'. The secondary L1: is connected to tubes V11 and V18 through resistance and condenser elements in such a manner that tubes V1-1-1a operate in quadrature relation. 1

The variable resistances R5 and R1 and the variable condenser Ca-4 permit of adjustment of the relative phases of the voltages impressed upon the tubes V11 1e in order that the proper sequence of operation may be secured in the tubes V-z-m.

The resistance Re serves to render the voltage across secondary L13 of transformer T14 independent of the adjusments of 03-4 or their respective resistances, and the resistances Ra-s and the condenser C5 serve at the receiver the same functions as those of Ra-a and C2 at the transmitter. The output transformers T15 and T16 correspond in connection and function with the transformers T12 and T1: in the sequence selector S in the transmitter. The tubes Vv-m are, therefore, actuated in synchronized sequence through conductors 6-9 connecting to the actuating grids G1' in the tubes V-i-m. Meanwhile, the incoming signal energy is continually being impressed upon control grids G3 01 the tubes V-z-m, and as the tubes are sequentially actuated, the signal impulses are selectively transmitted to the output transformers T'z-io which act, by virtue of their inertia, to smooth out the signal impulses into a substantially true reproduction of the signal.

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interiering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In an apparatus for receiving and rendering intelligible a multiplicity of continuous signals, a common input circuit, an electrondischargev device connected thereto and responsive only to sigmale of greater amplitude than the average maximum amplitude, a plurality of other normally sin operative electron-discharge devices, one for each or the received signals, and selective means controlled by said first-named device for rendering said last-named devices sequentially operative.

2. The method 0! transmitting a multiplicity of signals which consists in transmitting in sequence high frequency amplitude measurements 01 all of said signals and superimposing on each 10 recurring measurement of one only of said signals a flxed amplitude indication for synchronizing a receiving device with the transmission sequence.

3'. In a multiplex communication system, a transmitter including a plurality of signal input 15 circuits, an electron tube individual to each of said signal input circuits, said electron tubes each including a cathode, an anode, and a plurality of grid electrodes, a connection between each of said signal input circuits and one or said grid elec- 29 trodes in each of said electron-tubes, means for generating a recurring series of impulses of positive polarity by effecting a multiplicity oi different phase relations within each cycle of generated voltage, a connection between said means and another of thegrids' of each of said electron tubes for impressing a positive potential upon the said grids in successive order, a common output circuit connected between the plate and cathode of each of said electron tubes, 2. communication circuit, a connection between said common output circuit and said communication circuit whereby signal energy impressed upon said signal input circuits is successively transferred to said communication circuit in recurring time intervals at a rate determined by the positive potential impulses upon the said grids oif said electron tubes, and means for periodically superimposing a. synchronizing impulse upon the output of one of said tubes in said communication circuit in step with said recurring time intervals.

4. In a multiplex communication system, a transmitter including a plurality of signal input circuits, an electron tube individual to each of said signal input circuits, said electron tubes each including a cathode, an anode, and a plurality of grid electrodes, a connection between each of said signal input circuits and one of said grid electrodes in each of said electron tubes, an oscillator circuit, means for producing a series of impulses of positive polarity from each cycle of oscillation of said oscillator circuit, a connection between said means and another of the grids of each of-'s'a.id electron tubes for impressing a positive potential upon the said grids in successive 55 order, a common output circuit connected between 'the plate and cathode of each of said electron tubes, a communication circuit, a connection between said'common output circuit and said communication circuit whereby signal energy im- 50 pressed upon said signal input circuits is successively transferred to said communication circuit in recurring time intervals at arate determined by the positive potential impulses upon the said grids of said electron tubes, and means for periodically superimposing a synchronizing im-- pulse upon the output of one of said tubes in said communication circuit having an amplitude of positive potential which is greater than the maximum amplitude of the output of the others of said electron tubes.

5. In a multiplex communication system, a transmitting system comprising more than two signal input circuits, an electron tube circuit individual to each of said signal input circuits, s

common outputcircuit connected with all of said electron tube circuits, 9, communication circuit connected with said output circuit, an oscillator circuit, a sequence selector connected with said oscillator circuit for producing successive conditioning impulses for said electron tube circuits, means iorperiodically impressing an impulse upon the output of one of said electron tube circuits having an amplitude exceeding the maximum amplitude'of the output of the others of said electron tube circuits, a receiving system connected with said communication circuit, electron tubes connectedwith said receiving system and correspondlng in number to the number of signal input circuits in the transmitting system, a sequence selector in said receiving system, and means for controlling said sequence selector by the said impulse of excessive amplitude for successively conditioning each of the electron tubes in-sald receiving system for independently receiving signal energy impressed upon the signal input circuits in the transmitting system.

6. In a multiplex communication system, a receiving system comprising a multiplicity of electron tubes corresponding in number to the number of signal channels which may be impressed upon said receiving system, a sequence selector,

and means controlled by a synchronizing impulse of fixed magnitude periodically received simultaneously with the signals in one of said signal channels 10r actuating said sequence selector for rendering said electron tube circuits successively veffective for independently and sequentially responding to successive groups of recurring signal impulses.

7. In a communication system for the transmission of more than two separate signals over a common transmitting medium which includes a transmitter that produces a series of periodic potentials from each cycle of a single actuating oscillation, which signals are transmitted under control oi. the said periodic potentials and a receiver which produces a corresponding series of periodic potentials, the method of synchronizing the operation of the transmitter and the receiver which comprises superimposing on the measurements of one of the signals at the transmitter an impulse of constant amplitude, and impressing the said constant amplitude impulse on the means for producing the series of periodic potentials at the receiver whereby the said periodic potentials are produced in synchronism with those produced at the transmitter.

ALGER. S. RIGGS. 

